Has anyone experienced a rattle at idle? Sounds like a exhaust leak, and you can hear it thru to the tail pipes.

Could this be a defective hanger?

 

If these are 2007 cars take them back to the dealership ASAP. Diesels vibrate more in general but the Bluetec is very smooth with the balance shaft setup and should not vibrate or leak.

If you have no joy get your friendly mechanic to jack the car up and have a good look see yourself with engine running.

 

Nope, other than a (very) slight diesel clatter at idle, you would never know it's a diesel from the way it sounds. I would guess that the guys who did your PD might want to have another go at it. These problems should not make is past the factory and never past the dealer.

 

I have a 2008 320CDI and just recently the exhaust began to rattle very loudly at idle. I can't find anything external and the source seems to be from the interior of the exhaust just upstream from the mufflers. Pushing up slightly on the pipes at the rear axle increases the noise but I can't find anywhere that the pipes are contacting the body.

Anybody else had this problem?

 

I have this same issue - but rattles when cold - only 35 degrees F or less (thereabouts). It's coming from the drivers' side rear quarter panel, underneath, between the wheel and the rear bumper. It rattles until the car warms up, and then stops - like something is loose until it expands. It's loud, too... Into the dealer for the 4th time today - fortunately, it was originally reported under warranty (that has now expired), but they are covering the work under warranty. They replaced a missing bracket last time (not sure where that went); no obvious signs of an accident - no bondo, no sheet metal issues or undercarriage damage, and it was a CPO car.

It stops if I just put the tip of my shoe against the tip of the exhaust pipe - it has to be something heat-shield related, or a hanger that's not quite tight enough. At least I got it on video using my phone and was able to email it to the dealership. Good times - thankful for the service loaners.

 

My '07 450 was doing the same thing. When it was up on the lift getting brakes and rotors I noticed that the heat dsheild was bent downword and hitting on the muffler. As it is pliable, easy fix- just bend it back.

 

My 2008 did the same thing. Found bad exhaust hanger near tail pipe. Replaced 70K miles ago and no problems since.

 

I had the same problem rattling noise.It was heat dsheild.Had the service shop remove the plate vs replacing the catalytic convertor for 1700$.These merc is breaking by bank.Lots of issues.